Abnormal capacitance-voltage and switchable photovoltaic effect of epitaxial Mn-doped BiFeO3 thin film capacitor

Epitaxial BiFe0.95Mn0.05O3 (BFMO) film was deposited on (001)-oriented SrRuO3 (SRO) coated SrTiO3 (STO) substrate by radio-frequency (rf) magnetron sputtering. Indium tin oxide (ITO) was grown on BFMO/STO heterojunction to fabricate ITO/BFMO/SRO capacitor for investigating the ferroelectric and photovoltaic properties. The ITO/BFMO/SRO capacitor exhibits large remanent polarizations of 92.2 mu C/cm(2), 101 mu C/cm(2) and 109 mu C/cm(2) measured at 20V, 25V and 30V, respectively. An observed abnormal capacitance-voltage (C-V) curve can be explained based on the ITO/BFMO interface. The calculated capacitance and junction width of ITO/BFMO interface are 105 pF and 32 nm, respectively. Additionally, it is found that photovoltaic effect of the ITO/BFMO/SRO capacitor is mainly attributed to ferroelectric polarization and internal electric field induced by defects. The photocurrent densities coming from ferroelectric polarization and internal field are 36 mu A/cm(2) and 23 mu A/cm(2), respectively. The photovoltaic output from the ferroelectric polarization is obviously larger than that from the internal electric field.